My earlier U.S. Pat. Nos. 4,205,740, 4,044,876, 4,304,521 and 4,759,676 disclose pulsating gravity-type conveyors which are particularly desirable for conveying palletized loads, and which are also highly desirable for use in storage rack systems for permitting "first in-first out" storage of palletized loads. In this known conveyor or storage rack system, the loaded pallets are supported directly on conveyor rollers, which rollers are disposed in longitudinally adjacent relationship and are supported by a carriage or rail structure which enables the rollers to vertically reciprocate in a cyclic or repetitive manner. This arrangement physically causes the palletized loads to be intermittently lifted and lowered relative to a longitudinally-extending stationary brake which extends at a slight decline relative to the horizontal. The pallets are stopped by the brake when the pallets and rollers are in their lowered positions, whereas the slope of the roller arrangement enables limited gravity-induced forward advancing of the pallets when the rollers are in their raised positions.
While the known arrangement described above has proven highly successful for transporting and storing palletized loads, particularly in storage rack arrangements, nevertheless in some storage racks spacial or size requirements prevent maximizing the number of vertically stacked bays, or the use of long bays. For example, with known gravity-type systems of the type described above, the slope of the conveyor as it extends longitudinally along the bay typically involves a vertical drop of about six inches for each ten feet of horizontal conveyor length. Since such conveyors when incorporated into storage racks typically extend from a minimum length of about 40 feet to a maximum length of as much as 200 feet, the vertical drop over such lengths can vary from as little as about two feet to about ten feet. Because of this vertical drop, when several bays each incorporating a conveyor are stacked vertically on top of one other, the number of stacked bays is limited not only by the height limitation of the building, but also by the vertical drop caused by the slope of the conveyor. Thus, optimum utilization of available space, particularly vertical height, cannot always be achieved.
To improve upon arrangements of the type described above, my copending U.S.A. Ser. No. 07/859,221, now U.S. Pat. No. 5,228,819, illustrates therein a gravity-type conveyor or transporter which permits gravity-induced advancing of loads in a steplike manner horizontally along the transporter between input and output ends thereof, which transporter itself extends horizontally between the input and output ends. In this latter arrangement, the transporter is provided with a plurality of raceway elements which are aligned horizontally of the transporter and define sloped surfaces thereon which decline in the forward direction, with each sloped surface having a pad unit movably disposed thereon. The pad units in turn are adapted to engage loads, such as palletized loads, which are moved horizontally along the transporter. During upward lifting of the raceway elements, the pads engage the loads and lift them upwardly away from a support surface, whereupon gravity causes the loads and pads to move forwardly and downwardly along the sloped surfaces until the loads reengage the support surface. During subsequent lowering of the raceway elements, the pads disengage the loads and are spring urged rearwardly and upwardly along the incline so as to be positioned for reengaging loads during the next upward lifting of the raceway elements. The loads are thus intermittently engaged and gravity-moved forwardly in a steplike manner. With this arrangement, however, return movement of the pads upwardly along the inclined surfaces is effected by some type of driving device, such as springs. While the arrangement described above provides a desirable function and structure, nevertheless the present invention is believed to represent an improvement thereover by simplifying the overall structure and operation, while at the same time provide the same steplike gravity-induced horizontal advancing movement of loads.
Summarizing the invention, in a preferred embodiment thereof, the improved level gravity conveyor arrangement provides a plurality of individual load-engaging support pads disposed in generally aligned relationship longitudinally along the conveyor. The pads are movably supported on a series of runway segments which also extend longitudinally of the conveyor. Each runway segment defines thereon an upper raceway surface which movably supports the pad, which upper surface in the preferred and illustrated embodiment is defined by a plurality of support rollers mounted in longitudinally spaced relationship on the respective runway segment. The runway segments are alternately raised and lowered so that, when in a raised position, the upper surfaces slope downward in the forward direction. The pads engage and vertically lift the loads when the runway segments are in the raised position, whereby the weight of the loads causes the pads to move downwardly by gravity along the inclined upper surfaces to forwardly advance the loads through a small distance until the loads reengage a stationary support or brake surface. When the runway segments are lowered so that the pads disengage the loads, the pads are returned rearwardly along the raceway surfaces (that is, along the rollers) to their original position. The runway segments during raising and lowering are supported for angular displacement generally within a vertical plane which extends longitudinally of the conveyor so that, when in the lowered position, the upper raceway surface slopes or declines downwardly in the upstream direction to cause gravity-induced return movement of the pads to their original upstream positions. The runway segments are normally periodically raised and lowered in a cyclic manner to effect forward steplike advancing of the loads longitudinally along the conveyor.
In this improved conveyor arrangement, in the preferred embodiment, the conveyor is associated with a storage rack so that the conveyor arrangement is supported on a frame structure having supporting flanges which define the support or brake surface for palletized loads, with these flanges extending generally horizontally between opposite ends of the conveyor. When the runway segments are raised by a lifting device, such as an inflatable hose, the pads lift the loads upwardly away from the supporting flanges, whereby the weight of the loads causes the pads to move downwardly by gravity along the sloped raceway surfaces so that the loads are horizontally forwardly advanced a small amount until the loads again contact the supporting flanges. When the runway segments are lowered, the pads disengage the loads and are moved downwardly by gravity along the downwardly inclined raceway surfaces back to the upstream end of the individual runway segments so as to be positioned for engagement under the loads during the next lifting cycle.
With the improved arrangement of the present engagement, as briefly summarized above, both forward advance of the loads and return movement of the load-transfer pads occurs by gravity in a safe and controlled manner, and the overall structure can be simplified by not requiring any type of powered device such as springs or the like for returning the pads to the upstream positions. At the same time the overall transporter still retains its horizontal characteristics in that the conveyor still extends horizontally between the input and output ends and permits a maximum number of such conveyor units to be vertically stacked one above another within a storage rack while occupying a minimum overall vertical height.
The overall arrangement of this improved conveyor, briefly summarized above, is also desirable in that the support rollers are mounted on the runway segments and rollingly engage a downwardly-facing or bottom surface defined on the pads, which surface is generally protected due to its downwardly-facing orientation and prevents accumulation of dirt and contaminates thereon so as to maintain proper rolling engagement between the pads and rollers to provide for a more maintenance-free arrangement. The structural connections and cooperations of this improved conveyor also provide for increased simplicity of manufacture and assembly.
Other objects and purposes of the present invention will be apparent to persons familiar with this area of technology upon reading the following specification and inspecting the accompanying drawings.